Supporting-arm for radial drills.



W. T. SEARS.

SUPPORTING ARM FOR RADIAL DRILLS.

APPLICATION FILED OUT. 12, 1912.

1,098,981 w Patented June 2, 1914.

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By 5113A divrne W. T. SEARS. SUPPORTING ARM FOR RADIAL DRILLS.

APPLICATION FILED OCT- 12, 1912.

Patented June 2, 1914.

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FIT Years I be fully set forth in the following descrip- UNITED STATESPATENT OFFICE.

WILLARD T. SEARS, OF HARTFORD, CONNECTICUT, ASSIGNOR TO PRATT & WHITNEYCOMPANY, OF HARTFORD, CONNECTICUT, A. CORPORATION OF NEW JERSEY.

SUPPORTING-ARM FOR RADIAL DRILLS.

Specification of Letters Patent.

Application filed 0ctober,12, 1912.

of the principal objects of the invention be-' ing to provide a machineof this character having a drill-spindle supporting-arm which is strongin construction to thereby effectually adapt it to resist the bendingand the torsion due to vertical thrusts directed upwardly thereagainstinitially by the drill or equivalent tool when in action.

In the drawings accompanying and forming part of the presentspecification I represent one of the several forms of embodiment of theinvention which to enable those skilled in the art to practise the samewill tion. I do not, however, restrict myself to this disclosure; I maydepart therefrom in several respects within the scope of the inventiondefined by the claims following said description.

Referring to said drawings: Figure 1 is a top plan view of a radialdrill involving my invention. Fig. 2 is a side elevation of the upperportion of the same. Figs. 3 and i are transverse sections of thelines33 and M respectively of Fig. 1. Fig. 5 is a transverse sectional viewshowing an old type of supporting arm and my improved supporting armsuperimposed thereon.

Like characters refer to throughout the several views.

A radial drill usually comprises a vertical column, a supporting-arm,and a drillspindle carrying head, said arm being generally horizontallydisposed and supporting like 1 parts said head for adjustmentlongitudinally thereof. This head in addition to the drillspindle issupplied with the usual adjuncts for adjusting said head and thespindle.

When the drill is in operation on the work there is considerable upwardthrust applied to the spindle which in turn transmits the same to saidarm. Various ways have been devised for resisting the torsional andbending effects consequent upon this thrust.

Theoretically an arm in the form of a tube circular in cross section ispractically perfect; to resist torsion, it has its disadvantages,however. A drive shaft for rotating, through intervening gears orequivalent means, extends along said arm and when the same is acirculartube the shaft must of necessity be mounted outside the arm; thisconstruction is so complicated that its-practical or commercial use isstopped. This particular difiiculty has been overcome by making the armin the form of a part tube or of channeled form in cross section, thusmaterially decreasing its transverse area and providing at the same timea longitudinallyextending groove in which the shaft can be situated.Like this old type of arm my improved arm is in theform of a segment incross section. My arm though differs radishallower than that in the oldform, which is used in'casting the old type of arm and greatly increasethe resisting efl'ect thereof, both as to bending and torsionalstresses. While the groove in the front of the'arm is highlyadvantageous it may not in all cases be necessary, the invention notbeing restricted in this respect. By making the groove shallow as setforth I decrease the possibility of its collapse, making it thereby verystrong.

In the drawings the vertical column of the machine is denoted by 2 andit rises from a suitable base or other foundation (not shown). Thiscolumn constitutes the subject matter of a copending application filedOctober 2, 1912, Serial No. 725.416. The horizontal supporting arm isdesignated by 3 and it sustains for longitudinal adjustment thedrill-spindle head 4 equipped with and for also adjusting the rotarydrill spindle 5 which it is needlessfor me to describe. As will beperceived on reference to Figs. 3 and 4 said arm 3 is segmental in crosssection and is preferably although not necessarily hollow. By having thearm hollow I can make the same comparatively light without sacrificingnecessary resisting ability. The said arm is tapered progressively onits rear side toward its outer, although in all cases this is notessential. There is a rotary-shaft as 6 operable in practice from anelectric motor or in some other suitable way, for driving throughgearing or otherwise, the drill spindle 5, said shaft as shown extendinglongitudinally of the supporting arm 3 in the groove or channel 7 infront of said arm 3. It will be observed that the lower terminal portion8 of the arm 3 is back of the upper terminal portion 9 thereof by virtueof which I can give to the outer wall a greater outward bulge andthereby make the arm of greater extent from front to rear than thesegmental form of arm now in use without increase of weight or metal; asa result I increase the resisting power both as to bending and torsionalstresses, of said arm 3with respect to the old type. The upper terminalportion of said arm is provided with ways 10 for supporting the head 4for adjustment, the lower part of said upper terminal portion beingrabbeted as at 11 to receive the relatively fixed rack 12 constitutingpart of the adjusting means for said head.

It is desirable to note that the upper and lower terminal portions ofthe head supporting arm 3 have ways 15 and 16 for the slidable head 4:,these ways as shown being vertical, the plane of the front of the lowerway being back of the plane of the front of the upper way. In theconstruction shown the lower way 16 is a greater distance from the axisof motion of the spindle 5, than the upper way 15, this axis beingindicated by the dotted lines 17 in Figs. 3 and 4.

As already explained the lower terminal portion of the supporting arm isback of the upper terminal portion thereof. should also be stated thatthe metal resulting from the positioning of said lower terminal back ofsaid upper terminal can be distributed in the rear portion of said arm,for instance in the rear surface thereof by virtue of which said arm canbe made of greater cross sectional extent than the old form of armfbutwithout any increase in weight and metal. In the construction shown theresult is secured by making the radius of the rear surface of said armgreater than the radius. of the front surface or grooved portion thereofwhich, however, in ll cases maynot be, necessary, such for example aswhen the arm has no groove in its front.- This groove, however, ishighly advantageous in that it provides a space for thepower-transferring shaft 6 or equivalent. The mere setting of the lowerterminal back of the upper terminal of said supporting arm is in itselfhighly advantageous as in view thereof I can bring the axis of rotationof the spindle much closer in than is possi ble where the upper andlower terminals of the arm are in vertical alinement.

In Fig. 5 I have shown the new and old types of arms, denoted by 3 and 3respectively. One of the primary considerations in a supporting arm isthe ability thereof to resist the thrusts and torsion effects which thearm 3 does in a highly advantageous manner. This arm 3 is of the sameWeight and has the same amount of metal as the arm 3, but is materiallystronger, due to the fact that the lower portion or terminal of the arm3 is back of the upper terminal thereof, by virtue of which said arm 3or the outer wall thereof can be given a greater bulge or bow away fromthe axis of rotation of the spindle than is the case with the old arm.In other words in the new form of arm the increase in cross sectionalextent over the old is due to the fact that the lower terminal portionof the new form of arm is back of the upper terminal portion thereof,the difference in cross sectional extent representing the increase ofthrust and torque resisting ability of said new form of arm, and thiswithout increasing the weight or amount of metal in said new form of arm3. That is to say the metal displaced by setting the lower terminal backof the upper terminal of said arm 3 is distributed in the rear or backpart thereof.

What I claim is:

1. In a radial drill, the combination of a supporting arm havingseparate ways, a head slidable on said ways, and a rotary spindle on thehead,one of the ways being a greater distance from the axis of rotationof the spindle than the other way.

2. In a radial drill, the combination of a supporting arm havingsuperposed ways, a head slidable on said ways, and a rotary spindle onthe head, the lower way being a greater distance from the axis ofrotation of the spindle than the upper way.

3. A supporting arm for radial drills seg mental in cross section, thelower terminal portion of said arm being back of the upper terminalportion thereof, the metal resulting from the disposition of saidlowerterminal back of said upper terminal being distributed in the back partof said arm.

4. A supporting arm for radial drills segmental in cross section havinga groove on the front side thereof and the rear side being curved, theupper terminal of said arm being in front of the lower terminal thereof,the metal resulting from the disposition of said terminals beingdistributed in the rear surface of said arm, and said rear surface thisdisposition of said Ways being dis- 10 tributed in that part of the armfarthest from said axis of rotation.

In testimony whereof I afiix my signature in presence of two Witnesses.

WILLARD T. SEARS. Witnesses W. M. S'roRRs, H. M. KILBOURNE.

